This proposal outlines a plan to significantly improve current understanding of branched-selective asymmetric allylic alkylation reactions. This class of reactions has demonstrated utility in the asymmetric synthesis of pharmaceuticals. Challenges remain, however, that limit the application of these reactions to certain classes of substrates, particularly on a large scale. In the proposed study, quantum chemical methods will be used to gain a more complete understanding of the factors that dictate selectivity in these reactions. Specifically, the mechanisms of molybdenum- and iridium-catalyzed allylic alkylation reactions will be studied computationally to ascertain the steric and electronic origins of enantioselectivit and regioselectivity. Predictive models will be developed that can be applied to reactions of other catalysts and substrates. Finally, new catalysts will be designed computationally that are predicted to provide enhanced selectivity and efficiency. This study will significantly improve our understanding of this class of reactions and lead to further applications in the synthesis of biologically active compounds.